It all depends on how busy they are. I am told the slow season is May to October. I was in Cancun last year in October and felt like I practically owned the place. It was very slow. This past Labor Day was very slow in Coz. With the recession and gas prices and air fares going up, I think it is a safe bet you will have no problems without a reservation.
However, looking at it from the ops point of view, making a reservation does help them with their planning: letting staff know when they will be needed, allocating boats to divers, that sort of thing. If you are hoping to do some of the more challenging dives (Punta Sur, Barracuda, Maracaibo, Columbia deep) the shop will need to do some planning, but if you are with a conscientious operation, they problem wouldn't do those dives on your first day.
An kind of hidden advantage of a reservation for you is that you are committed. You are less likely to decide to sleep-in. (Although if you tied one on the night before, please sleep-in but call the shop and let them know you will be a no show. No sense pushing yourself when you are dehydrated and tired.)
However, looking at it from the ops point of view, making a reservation does help them with their planning: letting staff know when they will be needed, allocating boats to divers, that sort of thing. If you are hoping to do some of the more challenging dives (Punta Sur, Barracuda, Maracaibo, Columbia deep) the shop will need to do some planning, but if you are with a conscientious operation, they problem wouldn't do those dives on your first day.
An kind of hidden advantage of a reservation for you is that you are committed. You are less likely to decide to sleep-in. (Although if you tied one on the night before, please sleep-in but call the shop and let them know you will be a no show. No sense pushing yourself when you are dehydrated and tired.)
